Saikin Yatotta Maid ga Ayashii

After Yuuri's parents die, Lilith arrives to work as a maid in his mansion and becomes the only other person living with him. Yuuri is convinced there is something suspicious about her: she cooks too well, keeps the house impossibly clean, and smiles at him in a way that makes him suspect she has secretly enchanted him. Whenever he questions her, Lilith answers with teasing that only deepens his confusion.

What Yuuri cannot do is hide his thoughts. When he suspects Lilith has bewitched him with her beauty, he simply says it to her as if making a normal accusation. His "investigations" slowly become a string of innocent confessions, while Lilith's real secret proves to be less about magic than why she chose to return to this particular home.